Stormwater and wastewater floating treatment wetlands (FTWs) can contain plastic floating support systems. However, to date, there has been only one field study into whether a sole FTW was a potential source of microplastics in the environment. In this laboratory study, it was investigated whether floating support systems made from different types of polymers in different FTWs release microplastic when exposed to ultraviolet (UV) radiation. It was found that FTWs made from polyethylene terephthalate (PET; median release of PET=4.6  μg/cm2) released more microplastics than FTWs made from high-density polyethylene (HDPE; median release of HDPE=1.1  μg/cm2). Adding polyurethane (PUR) seems to cause a higher microplastic release from FTWs. Different UV exposures produced no obvious effect on microplastic release from the FTWs. Given the large variation of the data and the limited number of FTW samples, further studies on this topic are recommended.